Facile Deep and Ultradeep Hydrodesulfurization by the [(iPr3P)Ni]5H6 Cluster Compared to Mononuclear Ni Sources

The pentanuclear nickel cluster [(iPr3P)­Ni]5H6 facilitates the room-temperature hydrodesulfurization of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethydibenzothiophene. These reactions provide the new tetranuclear nickel hydride sulfide [(iPr3P)­Ni]4­(μ-H)4(μ4-S) (1). In comparison, the dinuclear dinitrogen nickel complex [(iPr3P)2Ni]2(μ-N2) undergoes oxidative addition of the C–S bonds of dibenzothiophene and 4-methyl dibenzothiophene to provide the metallacycles Ni3(PiPr3)3­C12H8S (2) and Ni3(PiPr3)3­C13H10S (3), respectively, but 4,6-dimethydibenzothiophene is unreactive, even with heating to 70 °C for a week. The reaction of [(iPr3P)­Ni]5H6 with SPiPr3 in toluene provided [(iPr3P)­Ni]5H6(S) (4), which was observed and characterized by NMR spectroscopy. The addition of vinyltrimethylsilane to 4 provided the best synthetic route to 1, with (iPr3P)­Ni­(η2-CH2CHSiMe3)2 (5) generated as a byproduct.